2, 6-dimethylnaphthalene-1-sulphonic acid and a process of preparing it



.diluted with about 1000 parts of water.

Patented F ch. 8, 1938 PATENT OFFICE 2,6-DIMETHYLNAPHTHALENE-l-SULPHONICACID AND A PROCESS OF PREPARING willy Schumacher,Frankfort-on-tlie-Main, Germany, assignor to General Aniline Works,Inc., New York, N. Y., a corporation of Delaware No Drawing. ApplicationJuly 6, 1936, Serial No. 89,249. In Germany July 4, 1935 2 Claims. (01.260159)' a 5 The present invention relates to2,6-dimethylinaphthalene-l-sulphonic acid and to aprocess of preparingit; more particularly it relates to a q compound of the followingformula: I 0.11

CHa

.;.Three monosulphonic acids of 2,6-dimethy1- naphthalene aretheoretically possible; two have been prepared and described inliterature, namely' the 2,6-dimethylnaphthalene-8-sulphonic acid 1 (cf.fBerichte der Deutschen Chemischen Gesell- .s'chaft, vol. 52, page 358)and. the 2,6-dimethylnaphthalene-'l-sulphonic acid (of. ibid, vol. 52, 3page 355 and Collect. Trav. chim. Tchecoslovaquief, 4.21-3 1, Jan.1932). The sulphonation of the 2,6-dimethylnaphthalene mentioned inGerman Patent No. 301,079, dated, August 3,

1916, likewise only leads to the 2,6-dimethylnaphthalene-8-sulphonicacid or, by transformation, to the 2,6-dimethylnaphthalene-7-sulphonicacid. a

' The 2,6-dimethylnaphthalene-l-sulphonic acid,

in which the sulphonic group stands in orthoposition to a methyl-group,has not hitherto been known. Weissgerber and Kruber mention is (inBerichte der- Deutscher Chemischen Gesellshaft, vol. 52, page 358), butthey did not succeed in isolating it or preparing it. Now I have foundthat the 2,6-dimethylnaphrthalene-lesulphonic acid is-obtained with agood yield by causing a sulphonating agent to act for stance, by meltingit with a caustic alkali.

- The following examples serve to illustrate the invention, but they arenot intended to limit it thereto, the parts being by weight:

1. '102 parts of cencentrated sulphuric acid or 98 parts of sulphuricacid monohydrate are I 1 caused to run, while stirring, withinhalf-an-hour ata temperature of about 110-120-C. into 78 50. parts ofmelted 2,6-dimethylnaphtha1ene. Stirring is continued for about 5 to .10minutes at the .same temperature; aftercooling, the mixture is Thesulphonic acid obtained is then dissolved by .55 heating, and thesolution is filtered in order to eliminate a small amount ofunsulphonated 2,6- dimethylnaphthalene. By addition of a small amount ofsodium chloride, up to 1 per cent., the very sparingly soluble sodiumsalt of the 2,6- dimethylnaphthalene-7-sulphonic acid, a smallproportion of which is also obtained is precipitated from the filtrate;by further addition of sodium chloride the sodium salt of the2,6-dimethylnaphthalene-l-sulphonic acid is obtained with a good yieldThe sulphochloride of the 2,6-dimethylnaphthalene-l-sulphonic acid,which can be prepared in the usual manner from the sodium salt of thesulphonic acid and phosphorus pentachloride, melts at 11611'7 C. Bycausing it to react with ammonia it can be transformed into thesulphamide, which melts at 124-125" C.

2. 78 parts of 2,6-dimethylnaphthalene are melted; parts ofchlorosulphonic acid are added drop by drop within 45 minutes at atemperature of 115 C. to 120 C., while stirring. Stirring is continuedat the Same temperature for about another 10 minutes and thesulphonation mixture is then diluted with about 1000 parts of Water. Theproduct is worked up as indicated in Example 1.

3. parts of fuming sulphuric acid containig 20 per cent. of sulphuricanhydride are caused to run, while stirring, within half-an-hour into'78 parts of melted 2,6-dimethylnaphthalene at v a temperature of C. toC. Stirring is continued at the same temperature for about another 5minutes and the sulphonation mixture is then diluted with about 2000parts of water. The product is worked up as indicated in Example 1.

I claim:

1. A process of preparing 2,6-dimethy1naphthalene-lesulphonic acid whichcomprises causing a sulphonating agent to act for a period of up toabout two hours on molten 2,6-dimethylnaphthalene.

2. The 2,6 dimethylnaphthalene-l-sulphonic acidof the following formula:

forming a sulphochloride which meltsat 116 C. to 117 C., and asulphamide which melts at 124 C. to 125 C.

WILLY SCHUMACHER.

